In recent years, the development of a power generating system using waste heat generated from plant facilities and power generating facilities is increased to build an energy saving society. In particular, accompanying increased industrial wastes and the like, the effective utilization of waste heat generated during the incineration thereof becomes an issue. For example, in a large-scale waste incineration facility, waste heat is recovered by heating a boiler with the waste heat, and generating electricity with a steam turbine. However, since small-scale and middle-scale waste incineration facilities which account for a large majority have high dependency on the advantage of scale, a method for generating electricity with a turbine cannot be utilized.
Therefore, as such a method for generating electricity with waste heat, a thermoelectric conversion element using a thermoelectric conversion material which reversibly performs thermoelectric conversion by utilizing the Seebeck effect or the Peltier effect has been proposed.
Further, Mg2Si which is nontoxic and present in a rich amount and has little environmental impact (e.g., see Non-patent Literatures 1, 2, and 3) has been studied as the thermoelectric conversion material. However, since in terms of production, it has disadvantage such as danger due to high chemical reactivity of Mg, synthesis in vacuum or in inert gases is required. Therefore, there have been problems such as about 8-hour preparation, trouble in synthesis, and expensiveness. Further, since unreacted Mg and Si elements remain in the synthesized Mg2Si, there have been problems such as low thermoelectric conversion performance and short life span.